Wideband Code-Division Multiple-Access (WCDMA) is one of the main technologies for the implementation of third-generation (3G) cellular systems. It is based on the radio access technique proposed by ETSI Alpha group and the specifications was finalised 1999.
The implementation of WCDMA is a technical challenge because of its complexity and versatility. The complexity of WCDMA systems can be viewed from different angles: the complexity of each single algorithm, the complexity of the overall system and the computational complexity of a receiver. W-CDMA link-level simulations are over 10 times more compute-intensive than current second-generation simulations. In W-CDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. UMTS networks need to support all current second-generation services and numerous new applications and services.
The WCDMA air interface has been standardized by 3rd Generation Partnership Project (3GPP) as a radio transport medium for global mobile communication systems. The specification allows superior user data rates and systems throughput capacities compared to any 2nd generation mobile communication standard. The adaptability of WCDMA system enables new ad significant evolutionary step in packet data access.
3rd Generation Partnership Project (3GPP), see for example 3GPP TS 25.433 V5.6.0 (2003-09): “Technical Specification Group Radio Access Network; UTRAN Iub interface NBAP signalling (Release 5)”, describes a procedure for handling Down Link (DL) power control, when handing over communication from one base station to another one, as illustrated in FIG. 1. FIG. 1 illustrates two cells 100a and 100b in a cellular communication network, such as a WCDMA. For each cell there is a radio access point 110a/110b. Access points in the UMTS-system are referred to as Node B. A Node B houses one or several radio transceivers and handles the radio-link protocols with the User Equipment (UE). Each Node B provides radio coverage in a specific area and therefore effectively defines one or several cells of the UMTS cellular system. In a large urban area, there will potentially be a large number of Node B(s) deployed. In the following, the access points are referred to as base stations 110a/110b, connected to a base station antenna 120a and 120b, respectively, transmitting and receiving signals to/from a transmitter device (User Equipment (UE)) 140. When handling over communication from one base station, e.g. 110a to 110b, the power between the base stations must be controlled and balanced. This means that the output power from the base station 110b is set to substantially the level of base station 110a. This functionality is obtained through the network control (UTRAN).
The downlink transmit power control procedure, controls simultaneously the power of a DPCCH and its corresponding DPDCHs. The power control loop adjusts the power of the DPCCH and DPDCHs with the same amount, i.e. the relative power difference between the DPCCH and DPDCHs is not changed. The relative transmit power offset between DPCCH fields and DPDCHs, is determined by the network. The TFCI, TPC and pilot fields of the DPCCH are offset relative to the DPDCHs power by PO1, PO2 and PO3 dB respectively. The power offsets may vary in time.
The patent documentation is silence about a solution according to the present invention. However, power balancing between base stations is considered, e.g.: U.S. Pat. No. 6,351,650 discloses forward power control during a soft handoff in a wireless communication system, accomplished by tracking each power command (PC) transmitted from a mobile unit to two or more base station transceiver systems (BTSs). Each BTS may interpret power commands differently due to noise. However, the power commands are relayed to a selector along with additional data transmitted in a conventional fashion. The selector determines the power levels of each BTS and transmits power charge commands to maintain power balance between the BTSs. The BTSs may transmit each PC command to the selector or accumulate several PC commands and send a PC history to the selector. The selector generates a reference PC history, which may be one of the PC histories transmitted from a BTS, a combination thereof, and the result of data processing on the one or more PC histories. Individual power change commands or the reference PC history is transmitted back to the BTS to adjust the transmitter output level of each BTS so that the BTSs are transmitting at compatible signal levels
A transmit power load balancing technique in accordance with WO 02/23936 is used to increase the overall communication capacity of a radio communications system without incurring substantial, additional control signalling. An overloaded connection in a first cell serviced by a radio network is detected, and a second nearby cell, which is not overloaded, is identified. For a radio use node that has a connection with the radio network, radio transmission from the first overloaded cell is prevented or at least avoided in the downlink direction from the radio network to the radio use node. Instead, a radio transmission associated with that connection is established or otherwise permitted from the second cell in the downlink direction to the radio use node. The prevented or avoided downlink radio transmission is a traffic transmission. On the other hand, downlink control signalling associated with the connection from the first cell to the radio use node is permitted.